Carbohydrates

Carbohydrates [C_nH_2mO_m]

Monosaccharides(reducing sugars)	Disaccharides(reducing sugars)	Polysaccharides
Glucose	Maltose	Starch
Fructose	Sucrose?	Glycogen
galactose	Lactose	Cellulose

Condensation reaction: It is a chemical reaction in which two simple molecules are joined together to forma larger molecule with the removal of one molecule ofwater.

Hydrolysis: It is a reaction in which a water molecule is needed to break up a complex molecule into simple molecules.

Benedict’s test (reducing sugars)

1. Add 2 cm³ of Benedict’s solution to 2 cm³ of foodsample in a test tube.
2. Shake the mixture.
3. Heat the contents in a boiling water bath for 5minutes

Iodine test (starch)

1. Add 2 cm³ of food sample to a clean test tube.
2. Add a few drops of iodine solution to the test tube.

Glycogen and starch are suitable as storage materials in cells because: They are insoluble in water, so they do not change the water potential in the cells.They are large molecules which cannot diffuse through cell membranes, so they will not be lost from the cell.They can be easily hydrolysed to glucose when needed, for example, in tissue respiration.Their molecules have compact shapes so they occupy less space than all the individual glucose molecules that make up a glycogen or starch molecule

Carbohydrates are needed: to provide energy for cell activitiesto form supporting structures (e.g. cell wall)for conversion into other organic compounds (e.g. amino acids and fats)to form nucleic acids (e.g. DNA)to synthesise lubricantsto synthesise nectar in flowers